undefined reference to `main' collect2: error: ld returned 1 exit status

This error message typically occurs when the linker is unable to find the main function in your program.

The main function is the entry point of your program, and it is where the execution of your program starts. If the linker is unable to find the main function, it will be unable to generate an executable file.

To resolve this issue, you need to ensure that your program has a main function defined. The main function should have the correct signature and should be defined in a source file that is included in the compilation process.

If you have multiple source files in your program, ensure that the file containing the main function is included in the compilation process and is being linked correctly.

Additionally, check the compilation and linking commands to ensure that they are correct and that all required libraries and dependencies are being linked correctly.